pass: ensure frame pointer register is saved #174
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mmcloughlin
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mmcloughlin
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| @@ -145,6 +145,7 @@ type Info uint8 | |||
| const ( | |||
| None Info = 0 | |||
| Restricted Info = 1 << iota | |||
| BasePointer | |||
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Not sure if this is the right property name. An alternative is to call it something like AutoSaveRestore. The distinction is naming it for what it is vs. what the Go assembler does with it.
| } | ||
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| if fn.LocalSize == 0 { | ||
| fn.AllocLocal(int(gotypes.PointerSize)) |
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For some reason adding pointer size seemed like the right idea. But should this just be fn.AllocLocal(1) instead?
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Codecov Report
@@ Coverage Diff @@
## master #174 +/- ##
=======================================
Coverage 79.49% 79.50%
=======================================
Files 56 56
Lines 30907 30919 +12
=======================================
+ Hits 24569 24581 +12
Misses 6192 6192
Partials 146 146
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Currently
avousesBPas a standard general purpose register. However,BPis used for the frame pointer and should be callee-save. Under some circumstances, the Go assembler will do this automatically, but not always. At the momentavocan produce code that clobbers theBPregister. Since Go 1.16 this code will also fail a newgo vetcheck.This PR provides a (currently sub-optimal) fix for the issue. It introduces an
EnsureBasePointerCalleeSavedpass which will check if the base pointer is written to by a function, and if so will artificially ensure that the function has a non-zero frame size. This will trigger the Go assembler to automatically save and restore the BP register.In addition, we update the
asmdecltool toasmvet, which includes theframepointervet check.Updates #156